Presently, standardization of a 4G wireless communication system is being developed in the 3GPP (Third Generation Partnership Project). According to the 4G efforts, improvement in a maximum communication rate and improvement in quality at a cell edge can be realized by using a technology such as relaying or carrier aggregation. Also, improving coverage by introducing a base station other than an eNodeB (macrocell base stations), such as a HeNB (which may also be referred to as a HeNodeB, a Home eNodeB, a femtocell base station, a small mobile phone base station, or the like; hereinafter, referred to as HeNodeB), a RRH (Remote Radio Head), or the like, is also being considered.
Furthermore, each eNodeB is provided with an X2 interface, and each eNodeB can communicate directly with another eNodeB via the X2 interface. Accordingly, each eNodeB can exchange information for Inter Cell Interference Coordination (ICIC), for example, with another eNodeB via the X2 interface.
Also, the HeNodeB is a small base station installed at home. Owing to the installation of the HeNodeB, a user equipment is enabled to communicate with the HeNodeB even within home where the radio wave of the eNodeB is weak. Furthermore, owing to the installation of the HeNodeB, an effect of reducing the load on the eNodeB can be expected, and thus the HeNodeB is ranked in the 4G as an important node.
Additionally, an FDD (Frequency Division Duplex) mode and a TDD (Time Division Duplex) mode are provided in the 4G. The TDD mode is a method for setting each of ten subframes forming one frame for uplink use or for downlink use. This TDD mode is described in Patent Literature 1, for example.